A number of treatment options exist for cardiovascular disease. These include medical treatment with drugs, various forms of intervention therapy such as balloon angioplasty, atherectomy devices, and bypass surgery. Some treatments, such as bypass or transplant surgery, are major medical procedures that entail significant risks to a patient during the surgical operation. In the case of transplants, a patient may have to wait for a prolonged period of time before another heart is available. For these and many other reasons, alternatives to major surgery are desirable. Such alternatives may be intended as comprehensive treatments or as palliative measures to sustain a patient until other treatments are available.
The present invention relates to transmyocardial revascularization (TMR). TMR is a procedure where one or more channels are made in the heart, in order to allow blood to perfuse from the ventricle into the channels and thereby relieve the effects of heart disease or coronary artery disease (CAD). As used herein, the "heart" primarily refers to the muscular tissue of that organ and specifically the ventricle, but can include any part of the organ. Such a procedure is generally described in, among other places, U.S. Pat. Nos. 5,125,924 (Rudko, 1992) and 5,125,926 (Rudko et al., 1992), which describe a pulsed laser system that purportedly overcomes problems associated with forming channels in a beating heart. Laser implemented TMR (also called laser myocardial revascularization or LMR) is also described in U.S. Pat. Nos. 5,389,096 (Aita et al., 1995) and 5,554,152 (Aita et al., 1996), which describe the use of an elongate flexible lasing apparatus to form channels within the heart. U.S. Pat. No. 5,389,096 describes creating a channel from the interior of the heart (endocardium) towards the exterior (epicardium), and stopping the channel before the epicardium is penetrated. U.S. Pat. No. 5,554,152 describes creating a channel from the epicardium through the myocardium and penetrating the endocardium. (As used herein, the "myocardium" encompasses both the epicardium and endocardium although the latter terms may be used for more specificity where appropriate).
None of the known prior art discloses TMR techniques that are not dependent upon a laser. U.S. Pat. No. 4,658,817 (Hardy, 1987) uses a combination of laser energy and mechanical penetration. While lasers may result in satisfactory TMR, they have a number of drawbacks. It is difficult to supply adequate power from external to a body, through a catheter, and to the lasing element. Shaping laser beams is difficult, if at all possible; indeed, none of the known prior art discloses a shaped channel in connection with TMR. Instead, lased channels appear to be tubular and have a constant width through the heart.
Electrosurgical devices have been developed that ablate tissue or other objects by the application of radio frequency (RF) energy. See U.S. Pat. No. 5,454,809 (Janssen, 1995). Further electrosurgical devices are disclosed in pending PCT Application No. US96/18466 titled "Medical Catheters for Ablation and Detection" of Janssen et al. While electrosurgical devices are disclosed, there is no teaching to suggest adapting such devices for TMR. The present invention overcomes limitations in TMR by providing an alternative device and method of use for forming channels within the heart.
U.S. Pat. application Ser. No. 08/777,928, commonly owned and copending herewith, describes a device and method (including several embodiments) for accomplishing transmyocardial revascularization. That application, and all other documents referred to herein, are hereby incorporated by reference.
U.S. Pat. application Ser. No. 08/882,947 titled "Applicator for Radio Frequency Transmyocardial Revascularization" describes a number of devices and methods for inserting electrodes within the myocardium. It is an object of the present invention to expand the effectiveness of that invention by creating fissures within the myocardium.